This SBIR project is designed to demonstrate and develop an improved composition for nanofibers especially suitable for surface modification and biomolecule binding for cell culture and tissue engineering applications. A new trifunctional photoactivatible crosslinker will be included with available biodegradable polymers to form nanofibers containing photogroups on the surface. Rapid and facile illumination will enable photochemical bonding to the fiber surfaces, to the polymers suitable for biomolecule immobilization or the biomolecules themselves without polymeric spacers. The Phase II work is expected to develop biodegradable scaffolds for tissue engineering, more biomimetic cell culture surfaces for cellomic and other living cell sensor systems providing more confident assessment of toxicity and pharmaceutical activities in drug development. Specific aims of this Phase I proposal include: 1) optimize the electrospinning conditions for preparing photoreactive polymer nanofibers; 2) demonstrate facile surface modification of the photoreactive nanofibers with biomolecule-binding spacer polymers; and 3) demonstrate and optimize immobilization on the nanofibers of a model protein, streptavidin, with superior functional loading density. [unreadable]